ESE's works engine tuner

[porttiming124]

ok thank you

[jfn2]

Hello Condyn
Sent you a PM. Thanks, jfn2

[TZ350]

.



Ok I need some help. I am hoping for some ball park general advice from the Free Tec 50 guys. What sort of rotary valve timing do they use. 24mm carb, 14,000 peak rpm. Thanks....

[wobbly]

Easy for you TeeZee , put in 140/90 into EngMod and work back till you loose power.

[TZ350]

Easy for you TeeZee , put in 140/90 into EngMod and work back till you loose power.

Thanks Wob. I was getting lost in the woods looking for a tree.

[Frits Overmars]

I am hoping for some ball park general advice from the Free Tec 50 guys. What sort of rotary valve timing do they use. 24mm carb, 14,000 peak rpm. Thanks....

You won't find many 24 mm carbs with the Freetech50 guys; 28 to 30 mm is common but I also know one or two good engines with 34s.
Wobbly's 140°/90° guideline may work well with a 24 mm carb, but closing the disc at 90° after TDC with a bigger carb can make your engine rather temperamental.

With EngMod2T you can of course work in either direction but on a real life engine working your way back from 90° would mean making a handful of discs. If you start with a closing timing of 75° aTDC you can modify one and the same disc till the lap times get worse (although engine power will still be increasing) and then you know the values for the optimum disc.

FYI: the Aprilia RSA had a 42 mm carb and 155°/89,5° disc timing and it produced maximum power at 13000 rpm; that's a mean piston speed of 23,6 meters per second.
I'm not sure if your 'peak rpm' means revs of maximum power or maximum revs but in any case 14000 rpm is rather modest. Most Freetech50 engines produce maximum power at around 14.500 rpm which equals a mean piston speed of 19,2 m/s, still a lot less than the RSA value, so I think it would be best to stay well within those RSA limits.

[porttiming124]

Hello. When I modify an engine I always rounded the corner between the reed valves in the direction of the transfers.
I saw a photo of a tm motor and had it leave the corner more square. Is that the purpose of improving the direction of flow to the transfers or just reducing the volume?
What do you think of it?

[Muhr]

You won't find many 24 mm carbs with the Freetech50 guys; 28 to 30 mm is common but I also know one or two good engines with 34s.
Wobbly's 140°/90° guideline may work well with a 24 mm carb, but closing the disc at 90° after TDC with a bigger carb can make your engine rather temperamental.

With EngMod2T you can of course work in either direction but on a real life engine working your way back from 90° would mean making a handful of discs. If you start with a closing timing of 75° aTDC you can modify one and the same disc till the lap times get worse (although engine power will still be increasing) and then you know the values for the optimum disc.

FYI: the Aprilia RSA had a 42 mm carb and 155°/89,5° disc timing and it produced maximum power at 13000 rpm; that's a mean piston speed of 23,6 meters per second.
I'm not sure if your 'peak rpm' means revs of maximum power or maximum revs but in any case 14000 rpm is rather modest. Most Freetech50 engines produce maximum power at around 14.500 rpm which equals a mean piston speed of 19,2 m/s, still a lot less than the RSA value, so I think it would be best to stay well within those RSA limits.

The rotary intake time area will be controlled by the RPM and diameter of the disc apart from the opening angles. What was / is the diameter of the RSA?

[wobbly]

Yo Frits/TeeZee - I suggested 90* as that is about as radical as I have ever seen/used on the Rotax 256 engines spinning to 14000 - usually using 88.
And the small 24mm carb would need plenty of timing to make power and revs. A 28mm HV Lectron would have a 24mm venturi but would flow hugely better than an OKI etc.
I know many FreeTech 50 guys use Lectron 30s - but remember the HV version of that has a 26mm venturi behind the slide to aid part throttle response.

The 140 opening I thought was about the limit as well, I have seen the Aprilia timing quoted up to 142 , and that caused more issues with tuning than it made Hp on the Rotax.
155 seems a completely crazy timing , and something I have never been aware of even having received several Aprilia EngMod files from people who have used thesis data from the Uni at Valencia for other
PhD projects.

Re relieving of the case in the TM is a long time mod. What is needed is to allow the side flow exiting the upper petals only to enter a slowly deepening channel as it heads for the transfer entry duct.
We attempt to bias the flow up under the piston with staggered reed stiffness , and this continues the idea.
There is a triangle shaped thin boss in the case on the reed box side walls, and the channel should start at nothing where the reed clamp is - then getting wider and deeper above this triangle that matches the reed block shape,
before radiusing around the corner into the transfer well above the crank.
TM engines are very finicky about case volume changes , especially going bigger , so dont get too excited.

[porttiming124]

With a v force would the channel really be just the top part of the reed box that would be pointing towards the transfer duct or the center as well? the 2nd image is what I tried earlier , thank you.

[wobbly]

With a VeeForce your idea looks perfect , if you wanted to try biasing the flow you could make the top hollowed out area deeper and or even higher.
Unless you can get varying petal thickness for this model its a bit harder to change the flow regime thru the tips.
We use different thickness petals and much different petal backups top and bottom.
After literally hundreds of dyno runs this was worth average 1.5 Hp in 50 over stock which was a pretty trick setup to start with.

[TZ350]

Blue line was with a 50 deg thermostat and the Red line was with a 42 deg thermostat. No other changes.

Put the RG50 up on the dyno tonight. Wanted to get a current base dyno run before putting this cylinder onto the rotary valve bottom end and doing a comparison run later in the week. Tests a week apart, not exactly back to back but you can only do what you can do.

[fpayart]

What was / is the diameter of the RSA?

Hello,

You will find hereafter pictures. The outside diamater of the valve is 126mm



The timing is 93° / 146°

Regards, Francis.

[Muhr]

Hello,

You will find hereafter pictures. The outside diamater of the valve is 126mm



The timing is 93° / 146°

Regards, Francis.

Thanks Good pictures!
Got this out of them.

Regards J

[wobbly]

Even allowing for scan errors , the 245 deg duration doesn't add up to 146/93 ?